1. Field of the Invention
The present invention relates to a method for manufacturing a bactericide consisting of an electrolytically treated liquid having high bactericidal action, prepared by the electrolysis (hereinafter sometimes referred to as electrolytic treatment) of raw water containing hydrochloric acid, as well as to an apparatus for manufacturing the same, the bactericide that has been manufactured by this method, and a method for sterilizing raw water.
More specifically, the present invention relates to a method for manufacturing a bactericide comprising an electrolytically treated liquid having high bactericidal action, prepared by electrolyzing raw water containing hydrochloric acid by means of an electrolytic cell with no diaphragm between the cathode and anode, and recovering the electrolytically treated liquid without separating it into anode water and cathode water. The invention further relates to an apparatus for manufacturing the same, the bactericide that is manufactured by this method, and a method for sterilizing raw water using this method.
In the specification, percentages are weight percent unless otherwise specified.
2. Discussion of Background
In the present invention, "electric power efficiency" means the amount of chlorine being generated per unit consumption electric power, a value obtainable by dividing the amount of chlorine being generated in an electrolytic cell by electric power consumed in the electrolytic cell.
Methods for obtaining acidic water or alkali ion water by the electrolysis of water have been known in general. Electrolytic cells are generally used when water is electrolyzed for the purpose of obtaining acidic water or alkali ion water (under the editorial supervision of Kunihiko Watanuki et al, Atarashii Mizu no Kagaku to Riyogijutsu, pp. 200-207, Science Forum Sha. (1992)). Conventional electrolytic cells are equipped with an anode and cathode in the interior and have a dual-structure in which the anode and cathode are separated by a diaphragm to divide the cell into an anode chamber and cathode chamber, and the electrolysis of water is performed by supplying water containing a small amount of an electrolyte such as common salt to increase the electrical conductivity to the electrolytic cell, and applying direct current to the electrodes to electrolyze the water.
The action of a conventional electrolytic cell is described. Water as the object of the electrolysis (hereinafter referred to as raw water) is first supplied by a pump or the like to the anode and cathode chambers of the electrolytic cell and is electrolyzed, but since in the anode chamber the raw water is subject to oxidation action, resulting in the removal of part of the hydrochloric acid ions in the form of oxygen gas, the water discharged from the anode chamber has high redox potential and is acidic, resulting in so-called acidic water. In the cathode chamber, on the other hand, the raw water is subject to reducing action, resulting in the removal of part of the hydrogen ions in the form of hydrogen gas, so the water discharged from the cathode chamber has low redox potential and is alkaline, resulting in so-called alkali ion water. The acidic water has bactericidal action and is used to disinfect and wash utensils, hands, and the like in the workplace in the food product industry, medical industry, and the like, while the alkali ion water is used for drinking.
Acidic water having bactericidal action has thus been produced by electrolytic treatment in recent years, and this water has been used as a type of bactericide.
Meanwhile, the various types of raw water used in our daily lives, factory equipment, and the like often need to be sterilized, therefore there has always been a desire for a more effective method of sterilization, and the above conventional electrolytic cells accordingly have been used for that purpose.
For example, with respect to cooling water, which is circulated between the condenser of cooling equipment in plants and the like and the cooling tower to which the condenser belongs so as to effect heat exchange, germs tend to proliferate in such cooling water, posing health problems. As such, a method for preventing such germs from proliferating by setting up an electrolytic cell in the piping through which the cooling water circulates has been adopted (see, for example, Japanese Patent Gazette for Laid-Open Patent Publication No. 5-87489 (1993)). A method for treating the water flushing through the toilet by using cisterns of flush toilets equipped with an electrolytic cell has been reported (see, for example, Japanese Patent Gazette for Laid-Open Patent Publication No. 3-33332 (1991)), and a method for utilizing water that has been electrolytically treated by an electrolytic cell has been frozen for use in the form of ice has been reported (see, for example, Japanese Patent Gazette for Laid-Open Patent Publication No. 7-218062 (1995)). In other known techniques, a method for sterilizing the stored water by using electrolytic cells set up in baths, pools, and the like has been reported (see, for example, Japanese Patent Gazette for Laid-Open Patent Publication No. 7-256262 (1995)).
Various techniques have been proposed for modifying the conventional method of electrolytic treatment described above (hereinafter referred to as Conventional Technique 1). For example, there have been reports relating to techniques which make good use of the water on the unused side of the acidic water or alkali ion water during the electrolytic treatment. The following conventional techniques are also known as techniques for mitigating scale on the cathode. That is, a method which comprises using means for exchangeably adding an alkali neutralizer or acidic neutralizer set up in the cathode and anode chambers of the electrolytic cell, and neutralizing the unused one of the resulting acidic water or alkali ion water, mixing it with the other, and a method for preventing scale on the cathode by reversing the polarity of the electrodes in the electrolytic cell at appropriate times to reverse the functions of the cathode and anode chambers are reported (see Japanese Patent Gazette for Laid-Open Patent Publication No. 4-99295 (1992); Conventional Technique 2).
The inventors earlier developed the following technique to remedy such problems, and have already filed for a patent. That is, they completed a technique which comprises adding hydrochloric acid to raw water in the cathode camber of the electrolytic cell to render the water acidic in advance, producing nearly neutral alkali ion water in the cathode chamber, and feeding back this water to the raw water (Japanese Patent Application No. 7-63384 (1995); Conventional Technique 3).
In another known technique, a method which comprises preparing raw water filtered, adding salt to the water, electrolyzing the water by a common method to obtain acidic water with pH of 1.5 to 3.3, and using this water as a bactericide (Japanese Patent Application No. 7-274921 (1995); Conventional Technique 4).
As another known technique can be mentioned a technique comprising electrolyzing a chlorine ion-containing liquid by a voltage of at least 10 volts to generate ozone together with chlorine and employing them for a bactericide (U.S. Pat. No. 3,616,355; Conventional Technique 5).
The Conventional Technique 1 described above suffers from the following problems, however.
1) Calcium and the like which are dissolved in the raw water adhere to form scale on the surface of the cathode and compromise the efficiency of the electrolytic treatment, making long-term operation difficult.
2) The diaphragm exposed to acid and alkali on both sides and electrified result in considerable wear and high running costs.
3) When only the acidic water is desired for use as a bactericide, the alkali ion water is discarded, and the water and electric power used for the alkali ion water are thus wasted.
In the aforementioned Conventional Technique 2, on the other hand, the method of reversing the functions of the cathode and anode in the electrolytic cell has been adopted to mitigate the problem described in 1) above, but a drawback is that the extra device for reversing the electrodes is required. In order to alleviate the problem in 3) above, a method for neutralizing the unused alkali ion water with an acid so as to reuse it has been considered, but since this water is merely prepared by adjusting the pH alone, thus obtained water has drawbacks in that other properties such as the redox potential are compromised, preventing the inherent effects from being obtained.
In Conventional Technique 3 described above, there is a disadvantage that problem 2) in the aforementioned conventional techniques, that is, the expensive running costs, cannot be remedied.
In Conventional Technique 4 described above, alkali ion water is produced at the same time as acidic water (bactericide), resulting in considerable expenditure of electric power and water, large quantities of electric power are required to obtain acidic water of low pH from neutral raw water, resulting in the high overall running costs, and equipment for filtering the raw water is also needed to prevent scale on the cathode and the like, tending to result in a complicated apparatus.
Conventional Technique 5 has the following problems a) to c) since it comprises generating ozone together with chlorine and utilizing them for sterilization:
a) The bactericidal action of chlorine is durable for a long period of time, but that of ozone decreases rapidly. Hence, in the case where the bactericidal action of a bactericide depends also upon the bactericidal action of ozone as in Convention Technique 5, the bactericidal action decreases in a short time and it is difficult to secure a stable bactericidal action.
b) Since oxygen is also generated simultaneously at the time of generating ozone, electric power for generating oxygen is wasteful.
c) Since ozone is hard to dissolve in water as compared with chlorine, it is easily diffused into the air, and a countermeasure such that ozone diffused into the air does not affect the human body, is necessary.
In methods for sterilizing raw water using conventional electrolytic cells, there have been no satisfactory methods of sterilization, since the conventional electrolytic cells are also plagued by the aforementioned problems 1) through 3).
As a result of painstaking research on a method for manufacturing a novel bactericide by electrolysis, in light of the foregoing conventional techniques, the inventors completed the present invention upon discovering that by introducing raw water containing hydrochloric acid into an electrolytic cell without a diaphragm between the cathode and anode, and electrolyzing the raw water containing the hydrochloric acid, the bactericidal action of the resulting electrolytically treated liquid could be dramatically improved, and this electrolytically treated liquid could be used as a bactericide having excellent bactericidal action.